b 1. Field of the Invention
The present invention relates to a multi-layer circuit board having layers of which relative positions are less dislocated and capable of keeping a circuit at a high precision, transmitting signals at a high speed and consuming less electric power, and to a manufacturing method of the same and application thereof.
2. Discussion On Related Art
A conventional multi-layer circuit board is generally produced by alternatively laminating and forming conductive layers and insulating layers. For example, there is a method by which inner layer members are integrally laminated through adhesive layers. Conventionally, the inner layer member is produced in such a method that half-thermosetting resin is applied to a reinforcing member such as glass fabric by impregnation to provide prepreg, the prepreg is laminated with copper foils placed on the upper and lower surfaces thereof to provide a copper bonded and laminated plate, and a circuit is formed by etching the copper foils. Further, said prepreg is used as the adhesive layer.
When the inner layer members are laminated and formed through the prepreg, a problem arises in that a lot of resin impregnated in the prepreg is flown by the pressure applied when lamination is effected, so that the respective inner layer members are dislocated with respect to each other and thus it is difficult to provide a multilayer circuit board having circuits kept precisely located therein.
In particular, as the circuit is microprocessed (to obtain a high aspect ratio), the solution of this problem is required. As a measure for solving it, there is proposed a method of laminating and bonding inner layer members including circuits whose surface is flattened by chemical plating through conventional prepreg [Japanese Patent Application KOKAI (Laid-Open) No. Sho 63-53996].
This method, however, does not sufficiently comply with the dislocation problem between the respective layers, since the prepreg is used as adhesive layers.
To solve the above problem, it is required to make the glass fabric used as the reinforcing member of the prepreg thinner to reduce an amount of the impregnated resin or to develop a new material for the adhesive layer which has an excellent reinforcing effect. There has been proposed a new reinforcing member used in place of the glass fabric which is composed of organic fiber such as polyamide, polyester, polyimide and the like.
Even if prepreg composed of the reinforcing member is employed as the adhesive layer, the problem of the dislocation between the respective layers is difficult to be solved. This is because when the glass fabric or the organic fiber sheet is used, varnish impregnated therein is flown out when it is laminated and bonded, and thus dislocation is easily caused.